Forty-eight hours after a surface-to-air missile shot down Malaysia Airlines Flight 17 over eastern Ukraine, killing 298 people on board, little progress is being made in securing its massive crash site, and the international investigation into the incident is being completely obstructed. Machine gun-wielding rebels stopped the Organization for Security and Co-operation in Europe Special Monitoring Mission in their tracks for a second day upon their arrival at the site Saturday afternoon. After negotiations, they were allowed some access to the site, but ordered not to wander off the roadway.